Aim of this paper is to decompose social background effects in upper secondary school choices into primary effects (related to differences in ability) and secondary effects (effect given ability) in Italy. We use the cross-sectional survey Percorsi di studio e di lavoro dei diplomati (ISTAT, 2004). A major issue to deal with is self-selection, as only secondary school graduates are interviewed. By employing the survey data together with administrative and census information, we derive estimates of the relevant distributions, correcting for selection bias. Our main finding is that secondary effects are substantial and substantially larger than in the other countries.